The invention relates to a linear drive comprising an elongated housing, whose interior space contains a drive part adapted to move in the longitudinal direction and furthermore has a longitudinal slot, which is provided with a sealing tape extending in the interior space, said tape being lifted clear of the longitudinal slot at the drive part by at least one guide face arrangement, said face arrangement facing away from said longitudinal slot, a longitudinal guide which is arranged outside the interior space and extends in parallelism to the same, a slide guided on the longitudinal guide for movement in the longitudinal direction, and an entraining member, which is secured to the slide, extends through the longitudinal slot to fit into a receiving socket open toward the longitudinal side of the drive part where it bears on axially aligned force transmitting faces.
A linear drive of this type is for instance disclosed in the European patent publication 0 113 790 B1. This known linear drive is of the fluid operated type and comprises a housing with an elongated interior space, which is open through a longitudinal slot to the outside. A drive part, in the form of a piston, running in the longitudinal direction in the interior space is connected by means of an entraining member, which extends through the slot, with a slide running on an external longitudinal guide. For sealing off the interior space the inner opening of the longitudinal slot is provided with a sealing tape, which is moved clear of the longitudinal slot by a guide face arrangement at the drive part in order to render it possible for the entraining member to extend through the slot. The entraining member itself is fixedly secured to the slide and a forked terminal part thereof extends into a receiving socket defined between two piston parts of the drive part, it being fitted around a central section of the piston and simultaneously bearing against axially aligned faces on the piston parts in order to ensure a coupling connection with minimum play between the piston and the entraining member.
The particular design of the known linear drive entails relatively elaborate production and assembly. Furthermore, the slide may only be dismounted in any necessary serving operations, for example for the purpose of replacement of components of the longitudinal guide, if the housing is taken to pieces with the result that the linear drive is out of unservice for some time.
Accordingly one object of the present invention is to provide a linear drive of the initially described type which is more particularly characterized by a simplification of production and assembly of the slide-entrainment member unit.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention the guide face arrangement is provided on the drive part and furthermore the part of the entraining member fitting into the receiving socket is in the form of an entraining finger having a free end thereof directed toward the sealing tape, such finger terminating short of the sealing tape section moved clear of the longitudinal slot.
Whereas in the prior art the guide face arrangement for the sealing tape is located on the entraining member, it is now a component of the drive part so that the entraining member may be coupled with the drive part without involving complex handling and manipulation of the sealing tape. In this connection there is a further simplification of assembly owing to the fact that the entraining member does not fit around the drive part on the radial side facing away from the longitudinal slot, and in fact has a simple entraining finger fitting into the associated receiving socket of the drive part and comes to an end short of the sealing tape section moved clear of the longitudinal slot by the guide face arrangement. Collisions between the entraining member and the sealing tape are now not possible and the necessary coupling between the entraining finger of the entraining member and the drive part may be ensured as a rule by simple plugging into and through the longitudinal slot. It is in this manner that it is possible for the slide and entraining member unit to be coupled in a relatively simple fashion with the drive part even when the sealing tape has already been fitted and fitting of the slide and the entraining member on the one hand and of the drive part and the sealing tape on the other hand may be performed separately without any trouble provided there is a suitable design. This furthermore facilitates any decoupling of the slide from the drive part which may be necessary for servicing purposes, since for this purpose the drive unit comprising the housing, the drive part and the sealing tape does not have to be taken apart.
Although the German patent publication 29,706,493.2 (utility model) discloses the feature of providing a guide face arrangement on the drive part itself serving for deflecting the sealing tape from the longitudinal slot, here the entraining member is an integral component of the drive part, something which necessitates a mutually separate manufacture of the drive part and of the entraining member.
Advantageous further developments of the invention are indicated in the claims.
In the case of one convenient form of the linear drive the drive possesses a guide channel defining at least one part of the guide face arrangement and having the sealing tape extending through it, and which extends more particularly with a clearance past the receiving socket on the side facing away from the longitudinal slot. In this respect a partition may be provided between the receiving socket and the guide channel, said partition preventing in all cases direct contact between the entraining finger and the sealing tape.
Since the entraining finger only overlaps or occupies a small part of the cross section of the drive part, it is more especially possible to have extremely compact transverse dimensions. In this connection it is quite an advantage in addition if the entraining finger, which preferably extends radially in relation to the longitudinally extending center axis of the drive part, ends short of such center axis.
The receiving socket itself may be constituted by groove-like recess in the drive part, which only extends over part of the periphery of the drive part, and for example is cut into the drive part like a notch or an incision.
In accordance with a further convenient development of the linear drive the entraining finger cooperates with the force transmitting faces via an elastomeric intermediate layer. It is in this manner that irrespectively of manufacturing inaccuracies it is possible at all times to ensure play-free contact between the entraining finger and the force transmitting faces in the axial direction of movement of the drive part and of the slide. Furthermore, these measures serve to allow a small degree of relative movement between the entraining finger and the drive part, such relative motion rendering possible a certain degree of decoupling and preventing jamming if the paths of movement of the drive part and of the slide are not exactly parallel to one another.
The entraining member is preferably attached in a releasable manner on the slide. This measure simplifies coupling between the entraining member and the drive part when the slide is already fitted to the longitudinal guide.
It is more particularly possible to make such a provision that the entraining member is mounted in such an adjustable fashion on the slide that in the case of a slide borne on the longitudinal guide it can be selectively positioned either in an extended setting fitting through the longitudinal slot into the receiving socket and a retracted setting outside the longitudinal slot. In this case there is the possibility of positioning the slide at the same axial level as the drive part when the entraining member is in the retracted setting and then by moving out the entraining member, more especially by hand, of plugging its entraining finger through the longitudinal slot into the receiving socket. By the reverse movement it is possible for the entraining member and accordingly the slide as well to be decoupled from the drive part again, for instance in order to perform any servicing operations which may be necessary.
In the case of a preferred modified embodiment of the linear drive, which more particularly renders possible a flat or low configuration, the longitudinal guide is located on a support plate connected with the housing and is opposite to that longitudinal side of the housing, which has the longitudinal slot. In this case the support plate is more particularly connected integrally with the housing so that the unit comprising the housing and the support plate may be produced economically as an extrusion, which is more especially made of aluminum material.
In principle it is possible for the linear drive for example to be so designed that its drive part may be caused to perform a linear movement by an electric motor. In this case the drive part could run on a lead screw extending in the interior space of the housing and coupled with an electric motor. However in most cases the linear drive will be designed as a fluid power unit, the drive part being constituted by a piston, which divides the interior space into two working spaces adapted to receive drive fluid, the linear motion being caused by suitably metered supply and/or removal of a drive fluid to and, respectively, from the working spaces. As a drive fluid compressed air is more particularly employed.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of embodiments thereof in conjunction with the accompanying drawings.